Fire Safety Science Digital Archive

The effect of an incident airflow upon the smouldering of beech sawdust has been investigated in detail. The sawdust was formed into small trains, as in earlier experiments under still-air conditions, and placed in a small wind tunnel; smouldering was then initiated by a small gas flame and the time of travel over unit distance (smouldering time) was determined. A logarithmic relationship was found between the smouldering time and incident air velocity; the effects of variations in train size, sawdust particle size, and moisture content upon this relationship were comparatively slight. The reduction in the minimum depth of sawdust necessary for sustained smouldering was also investigated and it was shown that this depth could be reduced easily to less than 3 mm. by an incident draught. Some further experiments, described in an Appendix, showed that flaming could be produced in wood shavings or newspaper in contact with the smouldering sawdust and that only gentle airflows are necessary. From these results it is concluded that an outbreak of fire could be a direct consequence of the initiation of smouldering in beech sawdust.